This project examines effects of hormones, drugs, and nutrients on thymus metabolism during early neonatal life. Current studies seek to: (1) identify factors and enzymes which regulate the phosphorylation of histones H1 and H2B, (2) determine the effectiveness of the factors in influencing the phosphorylation reaction as a funtion of the age of animals, and (3) define the physiological role of histone phophorylation in the development of thymus gland.